The present invention relates to bundle ties of the type including a tie strap and a tie head wherein the strap may be wrapped around an object or bundle and cinched or tensioned through the tie head to securely, lockingly engage the object. More particularly, it relates to a new and improved bundle tie head and tie system especially suited for use in outdoor environments which is characterized by low insertion forces and high withdrawal forces, as well as, high loop tensile strength.
Bundle ties are in widespread use for bundling together electrical wires or cables to form harnesses in telecommunications equipment, aircraft, more vehicles and the like. In U.S. Pat. No. 4,498,507, a bundle or cable tie is described which includes a plastic tie strap and a tie head having a pair of strap passages and a metal locking pawl. The housing is of a generally rectangular configuration including a solid block portion having a four-sided shroud projecting from one end defining an open recess. The strap passages are parallel to each other and extend along opposed sides of the tie head from the opposite entry end of the block portion into the shroud recess. The metal pawl is a stamped plate which is inserted through the recess into an intermediate parallel slot defined in the block portion. A deflectable locking tang on the pawl engages a shoulder in the slot to retain the pawl in the housing. Two slits are provided in the opposed free end of the plate to define a central tooth and a pair of spaced outer teeth which are oppositely bent away from each other so that the teeth are directed toward the opposed sides of the shroud adjacent a strap exit from the block portion.
In accordance with the design described in U.S. Pat. No. 4,498,507, the pawl is cantilever-mounted so that it is deflectable. Insertion of the strap end through one strap passage deflects the pawl toward the other strap passage. The strap is passed around the bundle to be tied and the second strap end is inserted into the second strap passage. During insertion of the second strap end, the strap must deflect the pawl out of its path, causing the opposed pawl teeth to engage the strap in the opposite passage. Continued insertion requires a deflection of the teeth against a compressive load which must be overcome. As a result, the overall design provides an undesirably high insertion force. Moreover, the points along the strap engaged by the pawl teeth form key stress regions where failure is expected to occur first, compared to other regions along the strap. In this patented design, these key stress regions are located in the open shroud area and are therefore undesirably exposed to adverse environmental conditions.
Another commerically available bundle tie arrangement of the environmental type includes a one piece cable tie head including a central partition wall and a pair of spaced-apart tie strap receiving passageways disposed adjacent opposed sides of the partition wall. A pair of independent pawl members are angled into each strap passage from an outer position in the housing. The pawls are inserted into an open top of the housing. The pawls have a pair of feet projections extending from opposed sides of the lower region thereon which must be stitched into small holes provided in a lower base wall provided in the housing. Thereafter, these feet are staked over to retain the pawl in the housing in a deflectable manner.
An advantage of this design over that described in U.S. Pat. No. 4,498,507 is that the insertion force associated with the insertion of each side of the strap is determined by the independent action of the pawl on that side of the tie housing, so that insertion of the first strap end does not disadvantageously increase the insertion force needed to insert the second end of the strap. As with the earlier design, this second design has an open strap-engaging contact area so that key stress regions are exposed to the elements under environmental conditions.
A further drawback common to each of the above designs is that they are relatively difficult to manufacture. Each of these pawl members include mounting features extending therefrom which must be properly aligned and positioned in a receiving structure in the housing. Moreover, insertion of the pawl in the housing is dedicated for one-way insertion, i.e., through the open side only, so that mounting of the pawls in the housings is a polarized function. This leads to a number of manufacturing disadvantages because equipment which ensures the proper orientation of the parts being fed into the pawl insertion equipment is required. This additional equipment increases the cost of producing the cable tie parts, which is reflected in product pricing.
In order to overcome the shortcomings of the prior art cable ties, it is an object of the present invention to provide a new and improved bundle or cable tie for use with a plastic tie strap exhibiting low insertion forces and high withdrawal forces for each side of the strap.
It is another object of the present invention to provide a new and improved bundle tie which is easy to assemble and inexpensive to manufacture which is capable of automated assembly.
It is a further object of the present invention to provide a new and improved bundle tie for use in outdoor environments wherein the key stress contact areas made between the tie head and the tie strap are protected from exposure to the elements.